In late December, the Federal Aviation Administration (FAA) issued a special airworthiness information bulletin (SAIB) on the prospective installation of angle of attack (AOA) indicators and systems on aircraft. The bulletin, which was issued on December 26 of last year, was titled Stall Warning System: Angle of Attack Alerting Systems.
It makes a simple recommendation to all general aviation aircraft owners and operators to ensure their aircraft is equipped with an AOA system of some kind, which gives numerous benefits to the aircraft owners and operators. The FAA stated in the bulletin, dated 2024-07, that these benefits could include a reduction in the risk of loss-of-control (LOC) incidents or accidents.
Special bulletin for an AOA recommendation
On Thursday, December 26th, 2024, the Federal Aviation Administration (FAA) issued a special airworthiness information bulletin (SAIB) called Stall Warning System: Angle of Attack Alerting Systems.
Specifically, this SAIB provides information to help general aviation aircraft owners and operators comprehend the significance and safety benefits of AOA alerting systems. The SAIB also applies to aircraft that are type approved under Part 23 standards, which is the category for standard airplanes.
The SAIB refers to an unpleasant aviation disaster that occurred on February 12, 2009, when a Colgan Air Bombardier DHC-8-400 aircraft crashed in Clarence Center, New York. The collision claimed the lives of four crew members, 45 passengers, and one person on the ground.
The National Transportation Safety Board (NTSB) investigated the accident and issued a number of findings about the cause of the incident. The NTSB determined that the captain’s incorrect response to the activation of the aircraft’s stick shaker, which shakes and vibrates the yoke to warn the flight crew of an impending aerodynamic stall, was the most likely cause of this regrettable incident.
The captain’s reaction to the stick tremor caused an aerodynamic stall that the plane was unable to recover from. The NTSB also disclosed several other contributing causes to this incident, including:
- Flight crew’s failure to monitor airspeed in relation to the rising position of the low-speed cue
- Flight crew’s failure to adhere to sterile cockpit procedures
- Captain’s failure to effectively manage the flight
- Colgan Air’s inadequate procedures for airspeed management during approach in icing conditions
Overall, the NTSB reached numerous conclusions about the incident. The NTSB specifically suggested that the FAA begin requiring the installation of low-airspeed alerting systems on all aircraft. This includes a technology that sends pilots redundant cautions about potentially hazardous low-speed conditions.
As a result, under SAIB 2024-07, the FAA formally recommends that all owners and operators of Part 23 aircraft, as well as those operating under Parts 121, 135, or 91, install and calibrate key AOA devices. The FAA also recommended that all owners and operators be trained on how to use AOA indications in their avionics systems.
What does an AOA indicator or AOA system do?
In general aviation aircraft, an AOA system measures and shows the angle at which a wing meets approaching wind. Essentially, this indicates how much lift the aircraft generates. As an aircraft’s lift drops, the likelihood of an aerodynamic stall increases.
So, mainly, an AOA system alerts pilots of an impending aerodynamic stall by alerting them to a crucial angle of attack. An AOA system aids pilots in maintaining safe flight conditions by providing a more precise stall warning than merely using airspeed measurements.
The AOA system is usually displayed on the cockpit instrument panel. It also usually employs lights or a gauge to convey visual alerts or cues to the flight crew. Some AOA systems additionally provide audio alerts when approaching a critical angle of attack, which may increase the system’s durability due to the redundant systems built in.
What are AOA indicators in aircraft?
AOA (Angle of Attack) indicators provide pilots with real-time information about the angle between the wing’s chord line and the relative wind. This helps prevent dangerous situations like stalls by ensuring pilots maintain optimal wing performance during flight.
Why is the FAA recommending AOA indicators for every aircraft?
The FAA recommends AOA indicators to enhance flight safety by reducing the risk of stalls, particularly during takeoff, approach, and landing phases. AOA indicators provide more reliable stall warnings than traditional airspeed indicators alone.
Are AOA indicators mandatory for all aircraft?
As of now, AOA indicators are not mandatory for all aircraft. The FAA’s recommendation is advisory, aimed at improving safety awareness and encouraging voluntary adoption.
What are the benefits of installing AOA indicators on aircraft?
Installing AOA indicators improves situational awareness for pilots, enhances safety by providing accurate stall margin information, and can prevent accidents caused by loss of control in flight.
How difficult is it to install an AOA indicator on an aircraft?
The difficulty of installing an AOA indicator varies depending on the type of aircraft. For modern general aviation aircraft, it typically requires minimal structural modifications, but proper installation and calibration by certified personnel are essential.
Are AOA indicators used in commercial aviation?
Yes, AOA indicators are standard in most commercial aircraft and are integrated into advanced flight systems. The FAA’s recommendation primarily targets smaller general aviation aircraft that may not already have them installed.
